Always Doing the Same Run
The human body is an incredibly efficient organism; it will always find the best way to do a task using the least amount of energy possible. Running the same route and pace day after day will stagnate your training efforts and cause you to burn fewer calories.
Any time we try a new activity, our bodies have to work a little harder to get it done. Once we've built up the muscle memory and our physiological and neurological systems have adapted to the particular demands, we become more efficient and use less energy.
The best way to overcome this is to change your running routine. Vary your route to include hills or uneven terrain. Include a good mix of tempo runs, hill repeats and speed intervals to push you above your maximum steady state pace and nudge your aerobic power (VO2max) higher. Wear a weighted vest or backpack. Try to make each run slightly different than the last one.
Just remember that more is not always better—scheduled recovery weeks help you avoid injury and also create the physiological adaptations that will allow you to run farther and faster in the future.
Moving Less the Rest of the Day
Some fascinating research has been done on the subject of NEAT (Non-Exercise Activity Thermogenesis)—the calories we burn during those waking hours when we are moving but not officially exercising.
Some of the more interesting studies, discussed in a 2013 article in Medicine and Science in Sports and Exercise, found that some individuals "compensate" to conserve energy after exercise by moving less throughout the rest of the day. This was found to be particularly true for older individuals and those who exercised at higher intensities. Since both of those qualifiers apply to many who run for weight loss, it's something to consider.
One of the best ways to determine if this is an issue for you is to buy or borrow a wearable activity tracker and use it for a few weeks. Pay attention to how many steps you take on days when you do and don't run. Subtract the number of steps you ran (or just don't wear the device when you run) and you'll see whether you tend to be lazier after a run.
Your total caloric expenditure will likely still be higher on days when you run. Be aware that you're giving back some of those calories in decreased activity over the rest of the day. If that's the case, make it a point to get up and move around a bit more on your running days.